1. Field of the Invention
This invention relates to an elasto-plastic damper for absorbing vibration energy which a structure such as a building and facilities possibly receives from earthquake motions and ground vibrations.
2. Description of the Prior Art
A typical application of elasto-plastic dampers to a structure such as a building and facilities is a vibration isolation mechanism, and various shapes of elasto-plastic dampers have hitherto been proposed. Generally, this vibration isolation mechanism comprises multi-layer rubber supports, and dampers, etc. which are disposed between the foundation and the upper structure of the building in order to reduce vibrations of the upper structure which are possibly created by earthquake motions and other ambient vibrations. NIKKEI ARCHETECTURE issued Dec. 30, 1985 by Nikkei-McGraw Hill, Inc. discloses various kinds of vibration isolation mechanisms, some of which are still under research. This publication also discloses a variety of types of dampers for vibration isolation, such as a viscous damper employing a viscous substance (asphalt silicone oil), a cylinder-type oil damper, an elasto-plastic damper employing a soft steel rod, a coil-type elasto-plastic damper, an elasto-plastic damper having a support as a guide for deformation of a steel rod, and a damper having a steel rod built into a multi-layer rubber support.
However, oil dampers and viscous dampers require maintenance, are difficult to design, and are limited in energy absorbability. Particularly, the oil damper has limited directional capabilities. Prior art elasto-plastic dampers using soft or rigid steel rods are also limited in energy absorbability. Furthermore, prior art elasto-plastic dampers are complex in shape, large and difficult to design.